The present invention relates to a fuel cell system and method, and more particularly, to a fuel cell system and a method of controlling the same effective for removing water accumulated in an electrolytic membrane during operation of a fuel cell without reduction in an operating performance of the fuel cell.
In a fuel cell system, water usually accumulates in the vicinity of electrolytic membranes of a fuel cell stack during production of electric power, blocking fine pores of the electrolytic membranes and deteriorating operating performance of the fuel cell stack. To solve this situation, it has been proposed to cyclically purge the fuel cell with air or nitrogen gas for removing water from the fuel cell stack.
In Japanese Patent Application Laid-Open Publication No. H7-235324, it has been proposed to detect wet condition of electrodes, namely, electric resistance variation at the electrodes to purge the fuel cell stack with oxygen gas for thereby exhausting water outside.
Since, however, such a fuel cell is not operated so as to cover various operating conditions of a moving object powered by the fuel cell stack during purging operation of the fuel cell stack with suitable gas such as air in order to remove product water, there exists a situation in which electric power to be produced by the fuel cell stack is limited.
In the fuel cell powered moving object such as electric automotive vehicle, operating load varies in a wide range, and driving performance of the electric vehicle is deteriorated due to insufficient amount of electric power output produced by the fuel cell system. To solve this situation, it is required that an additional secondary battery is undesirably required to augment the insufficient electric power output, thereby lowering fuel consumption.
It is, therefore, an object of the present invention to provide a fuel cell system and a method of controlling the same for removing water from a fuel cell stack without deteriorating driving performance of the moving object and the operating performance of the fuel cell system.
In the present invention, a fuel cell system applied for a moving object, is provided with: a fuel cell; a first flow control valve controlling flow rate of oxygen containing gas to be supplied to the fuel cell; a second flow control valve controlling flow rate of hydrogen containing gas to be supplied to the fuel cell; and a control unit opening the first flow control valve and the second flow control valve to supply the oxygen containing gas and the hydrogen containing gas into the fuel cell as purge fluid to remove water from the fuel cell in response to load condition of a moving object.
In other word, a fuel cell system of the present invention is provided with a fuel cell; a first flow control means controlling flow rate of oxygen containing gas to be supplied to the fuel cell; a second flow control means controlling flow rate of hydrogen containing gas to be supplied to the fuel cell; and a purge means activating the first flow control means and the second flow control means to supply the oxygen containing gas and the hydrogen containing gas into the fuel cell as purge fluid to remove water from the fuel cell in response to load condition of a moving object.
Besides, a method of controlling a fuel cell system of the present invention is for a moving object powered by the fuel cell. The fuel cell system having a first flow control valve controlling flow rate of oxygen containing gas to be supplied to the fuel cell and a second flow control valve controlling flow rate of hydrogen containing gas to be supplied to the fuel cell. The method obtains load condition of a moving object and supplies the oxygen containing gas and the hydrogen containing gas into the fuel cell as purge fluid to remove water from the fuel cell in response to the load condition of the moving object in response to the load condition of the moving object.
Other aspect and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.